Yttrium, dysprosium and ytterbium alkoxides



United States Patent 3,356,703 Y'I'IRIUM, DYSPROSIUM AND YTTERBIUMALKOXIDES Khodabakhsh S. Mazdiyasni, Dayton, Charles T. Lynch,

Fairborn, and Jonathan S. Smith I], Dayton, Ohio, assignors to theUnited States of America as represented by the Secretary of the AirForce N0 drawing. Original application Mar. 19, 1965, Ser. No. 441,388,new Patent No. 3,278,571, dated Oct. 11, 1966. Divided and thisapplication Aug. 23, 1965, Ser. No. 481,987

The portion of the term of the patent subsequent to Oct. 10, 1983, hasbeen disclaimed 6 Claims. (260-4291) ABSTRACT OF THE DISCLOSURE Metalcompounds of Y, Dy or Yb, combined with alkoxides or isopropene oxide.These compounds can be decomposed to form the corresponding metaloxides, useful as coating agents.

The invention described herein may be manufactured and used by or forthe United States Government for governmental purposes without thepayment to any of us of any royalty thereon.

This application is a division of our copending application Ser. No.441,388 filed Mar. 19, 1965, now US. Patent No. 3,278,571.

This invention relates to new compounds definable as alkoxides ofyttrium, dysprosium, and ytterbium, to methods of producing the same,and to the decomposition thermally or hydrolytically of these alkoxidesto high purity, fine particle yttrium oxide, dysprosium oxide, andytterbium oxide.

An object of the present invention is to describe the novel processesfor making alkoxides of the rare earth metals dysprosium, Dy of atomicnumber 66, and ytterbium, Yb of atomic number 70, and inclusive of thetransition metal yttrium, Y of atomic number 39 and the decomposition ofthe alkoxides to high purity oxides. Due to the lanthanide contraction,the reactions and properties of Y, Dy, and Yb compounds are expected tobe similar. Their ionic radii are 0.92, 0.92, and 0.85 A. respectively.They are all trivalent with electronegativities of 1.11, 1.1 0, and 1.06respectively. Their alkoxides differ from those of trivalent aluminumwhich has an ionic radius of 0.51 A. and an electronegativity of 1.47.Because of differences in atomic size and bond polarity, many of thereactions employed for the alkoxides of Y, Dy, and Yb are significantlydiiferent from those of Al. [In the short form of the periodic table Aland Y are both Group III, but one has d-electrons (Y), and the otherdoes not (Al).]

The products made are useful as precursor materials in the preparationof fine powders, films, and coatings of the oxides. The alkoxidesdecompose quantitatively to the oxides. The fine powders are useful inthe stabilization of zirconium oxide, in the preparation of electronicinsulators and oxidation resistant coatings, in clinical biochemistry,in adsorbents and catalysts, and the like. The products also are usefulin forming stabilized high-temperature ceramic bodies and oxidationresistant coatings. The alkoxides may also be used in makinghigh-temperature inorganic polymers.

The yttrium, dysprosium, and ytterbium alkoxides are compounds of thegeneral formula M(OR) where M is the metal and R is an organic group,such as, an alkene, alkyl or aryl, substituted or unsubstituted. Thealkene group is a hydrocarbon of the ethylene series with a free3,356,703 Patented Dec. 5, 1967 The previous available general methodsof making alkoxides of transition metals, such as by reacting metalhalides, with alcohols and ammonia in benzene, do not work when yttrium,dysprosium, or ytterbium are employed. The reaction of yttrium,dysprosium, and ytterbium with stoichiometric amounts of mercuricchloride and alcohols, which has also been employed to make otheralkoxides, does not yield high purity alkoxides or alkene-free alkoxidesof these metals.

The isopropoxides here of interest are made by reacting the metal withisopropyl alcohol under reflux with HgCl as the catalyst. The termcatalyst in this disclosure is defined as providing an alternate routefor the reaction and thus accelerating the desired reaction and makingit go to completion. It is not important whether the catalyst actuallyenters into the reaction or not. The amount of the catalyst HgCl isextremely important in the preparation of the high-purity productscontemplated hereby. Alkoxides with the heavier molecular weight Rgroups such as the tertiary butyl group (CH C and the 2-hexoxy groupHgClg catalyst The action of the HgCl is believed to be:

M+HgCl +3ROH M(OR) +Hg+2HCl-|-%H (2) with the free mercury formedcontinuing to act as a catalyst, as:

The amount of HgCl that is used is 0.01 mole or less per mole of metal.If larger amounts of mercuric chloride are used a side reaction takesplace to form alkenealkoxides where the mercury partially reduces thealkyl to an alkene, such as, from This reaction has been confirmed byinfrared spectra, nuclear magnetic resonance spectra, and the like.

When a stoichiometric amount of the mercuric chloride is employed ascatalyst, using reflux times of 48 hours or longer, the reaction goes tocompletion for forming the alkene-oxide. The reaction is:

The formation of the alkene-oxide has also been confirmed by infraredspectra and the like.

For the isopropoxide formation, the use of more HgCl than necessary,produces a product that is contaminated '3 9 with chlorine which is verydiflicult to remove from the product. This contamination occurs evenWhere the excess is 0.1 mole HgCl per mole of the metal.

The purification of the isopropoxides so produced is accomplished aftertheir filtration from the hot reaction mixtures by theirrecrystallization from hot isopropyl alcohol.

An alternative 'method for the preparation of the isopropoxides ofyttrium, dysprosium, and ytterbium is to react the anhydrous metaltrichloride with the alkali metal organic salt lithium isopropoxide asfollows:

THF 3LiOR You Y(OR)3+3LiC1 :ROH

The reaction is carried out in a medium of isopropyl alcohol (ROH) andtetrahydrofuran (THF) at 45 C. After 3 hours reaction (reflux), thealcohol and tetrahydrofuran are distilled off at reduced pressure. Theproduct is dissolved in :benzene filtered to remove LiCl, and againdried under reduced pressure. The isopropoxide product is furtherpurified by recrystallization from hot isopropyl alcohol. This reactionis generally carried out using stoichiometric amounts of the reactants.This facilitates purification of the product.

The heavier alkoxides cannot be made quantitatively directly from themetals or metal halides. An alcoholysis -method is employed to replacethe isopropyl group with with a heavier R group in this manner. Thegeneral formula is:

The reaction is done in excess R'OH and C H and is driven to completionby driving off the azeotrope. In the Equation 8 the composition of theazeotrope ROH-nC H varies with the alcohol ROH and, hence the remainderof the azeotropic compound is indicated by nC H The rise in thetemperature of the boiling azeotropic reactants ROH-nC H in the reaction(8) or of the in reaction (7 indicates the completion of the reaction.The product is purified 'by recrystallization if the product is a solidand by redistillation if the product is a liquid.

A limited number of heavier alkoxides of yttrium, dysprosium, andytterbium have been made by an ester exchange reaction as follows:

The reaction is carried out in an excess of the acetate, R OOCCHg, underreflux for 4 to 24 hours at the boiling point temperature of thelower-boiling acetate,

ROOCCH The product is purified after distilling oif the ROOCCH byrecrystallization if the product is a solid and by redistillation if theproduct is a liquid. This reaction however, does not produce high yieldsof the heavier alkoxides as do the alcoholysis reactions. Yields areless than 50% theoretical generally compared with yields of 70% or morefor the alcoholysis reactions.

In the experimental production the isopropoxides of yttrium, dysprosium,and ytterbium havebeen made in quantity as the alkoxides: Y(OC3H7)3,Dy(0C H and Yb(OC3H7)3. It is believed that the partial decomposition ofthe isopropoxides during handling in the analytical procedures isevidenced by high residue and metal percentages when the productpercentages are compared with the theoretical values, since the oxide isa decomposition product and the carbon and hydrogen in the productpercentages are correspondingly lower than theoretical values. When verycareful handling procedures have been followed by the analysts, resultsindicate a purity in excess of 99% theoretical. In this instance thepercentage of free oxide in the product alkoxide can be considerednegligible.

Alkoxides that have been made by the process that is disclosed hereinillustratively are:

Yttrium isopropoxide Y(OC H Yttrium isopropene-oxide Y(OC H Yttriumtert-butoxide Y(OC H Yttrium sec-pentoxide Y(OC H Yttrium sec-hexoxideY(OC H Yttrium tert-heptoxide Y(OC H Dysprosium isopropoxide Dy(OC HYtterbium isopropoxide Yb(OC3H7) Also all other isomers of the C H C Hand C H have been synthesized. For example, yttrium nbutoxide,sec-butoxide, and tert-butoxide and the like. Innumerable otheralkoxides can be made by the described procedures.

The alkoxides thermally decompose quantitatively to the oxides inextremely high purity. The reaction is as follows for yttriumisopropoxide:

A 2Y(OC3H7)3 Y203 303117011 30 11 (10) Y(OC H ZOO-210 C. at 0.1mm. Hg.

Dy(OC H -200 c. at 0.17 mm. Hg. Yb(0C H- 190-200 c. at 0.2 mm. Hg.

In the same manner of decomposition on a hot substrate, thin filmcoatings of the respective oxides can be prepared.

Hydrolytic decomposition results in the formation of oxy-alkoxy andfinally oxides of yttrium, dysprosium, and ytterbium from the alkoxidesas'follows:

M(OR)3 HOH MO(OR) ZROH oxy-alkoxy 2M(O R)3 3HOH M203 GROH 2M0 (OR) HOHM10 2ROH (13) The oxide is recovered as a finely divided high purityproduct.

A unique reaction to form mixed oxides from the mixed alkoxides can' beaccomplished because the alkoxides of yttrium, dysprosium, and ytterbiumcan be dissolved in liquid alkoxides of other metals acting as solvents.For example, yttrium 2-hexoxide which is a gummy liquid (semi-solid) isdissolved in zirconium tetra-tertiary butoxide, Zr(OC I-I which is aliquid at STP. Water is added dropwise with vigorous stirring to assurerapid dispersal of the water leading to rapid and complete hydrolysis.The oxides precipitate from the resulting alcoholic solution as finelydivided, homogeneous, intimately mixed oxides.

Up to 6 mole percent yttria (Y O in zirconia (ZrO mixtures prepared bythis method were calcined at 1000 C. The resultant powder was stabilizedin the cubic phase of zirconium oxide. The calcined powder was thencoldpressed and sintered at 1450 C. which resulted in the formation of avery high density (97-99% theoretical density) body. Normally yttriadoes not fully stabilize zirconia below 18 002000 C., and commercialyttriastabilized zirconia cannot be sintered to high densities below1800 C.

Alternative methods of forming mixed alkoxides are to dissolve theyttrium, dysprosium, and ytterbium alkoxides and other metal alkoxidesin a mutual solvent such as 'benzene, tertiary butyl acetate, and thelike. These mixtures are then hydrolyzed to form the mixed oxides. Anexample of this is the solution of yttrium isopropoxide and zirconiumisopropoxide Zr(OC H in benzene followed by hydrolysis.

It is to be understood that the processes that are described herein areillustrative of successfully operative procedure and that limitedmodifications may be made therein without departing from the spirit andthe scope of the present invention.

5 propene oxide.

2. The compound yttrium isopropoxide.

3. The compound yttrium tert butoxide.

4. The compound dysprosium isopropoxide. 5. The compound ytterbiumisopropoxide.

6. The compound yttrium isopropene oxide.

References Cited UNITED STATES PATENTS 10/1966 Mazdiyasni et a1.260-4292 OTHER REFERENCES Lynch et al.: American Chemical Society,Abstracts of Paper, 148th meeting, Aug. 31 to Sept. 4, 1964, page 17B.

20 L. DEWAYNE RUTLEDGE, Primary Examiner.

LELAND A. SEBASTIAN, Examiner.

1. A COMPOUND SELECTED FROM THE GORUP CONSISTING OF YTTRIUM,ISOPROPOXIDE, YTTRIUM TERT.-BUTOXIDE, DYSPROSIUM ISOPROPOXIDE, YTTERBIUMISOPROPOXIDE, AND YTTRIUM ISOPROPENE OXIDE.